Thanks for all the replies. I really appreciate everyone's willingness to share their knowledge.
It sounds like this could be a rather delicate operation...getting that tiny hole placed just barely above a wafer-thin piece of brass. If I screw it up, there's always JB Weld, right?!?! :p
I'm wondering why this GMC carb didn't have the vacuum advance port in the first place. Is there some other way of advancing/retarding the spark besides the vacuum advance? Just curious...
Thanks again,
Steve
